Wood, when burned, creates ash which floats through the atmosphere of the kiln and falls on the surfaces of the pots. The ash then melts, due to the temperature of the pots, and creates an ash glaze. All clay has to be heated (fired) to become hard, and wood fired pottery is the oldest method of firing clay. The work fired in this type kiln takes 2-3 days of stoking (putting wood in the kiln) in 5-10 minute intervals in order to achieve a maximum temperature of 2400 degrees, making the clay vitrify or harden into a glass.